1. Field of the Invention
This invention relates to thermally-coated veneer ties and associated anchors and anchoring systems for cavity walls. More particularly, the invention relates to anchoring systems with veneer ties having a thermally-isolating ceramic or ceramic-based coating and associated components made largely of thermally conductive metals. The system has application to seismic-resistant structures and to cavity walls requiring thermal isolation.
2. Description of the Prior Art
The move toward more energy-efficient insulated cavity wall structures has led to the need to create a thermally-isolated building envelope which separates the interior environment and the exterior environment of a cavity wall structure. The building envelope, while primarily designed to maintain structural integrity, is further designed to: (1) control temperature; (2) minimize thermal transfer between the wythes; and (3) remove moisture from the cavity. Insulation is used within the building envelope to reduce thermal transfer thereacross, maintain temperature and restrict the formation of condensate within the cavity. When the prior art metal anchoring systems are used, the integrity of the insulation is compromised. Such systems are constructed from thermally conductive metals that result in thermal transfer between and through the wythes. The use of the specially designed and thermally-protected veneer ties of the present invention lower the veneer tie thermal conductivities, provide an in-cavity thermal break, and thereby reduce thermal transfer.
When a cavity wall is constructed and a thermal envelope created, hundreds, if not thousands, of wall anchors and associated ties are inserted throughout the cavity wall. Each anchor and tie combination forms a thermal bridge perforating the insulation and moisture barriers within the cavity wall structure. While seals at the insertion locations deter water and vapor entry, unwanted thermal gains and loss still result. Further, when each individual anchoring systems is interconnected veneer-tie-to-wall-tie, a thermal thread results stretching across the cavity and extending between the inner wythe to the outer wythe. Failure to isolate the steel components and break the thermal transfer, results in heating and cooling losses and potentially damaging condensation buildup within the cavity wall structure. Such condensation buildups provide a medium for corrosion and mold growth. The use of thermally-isolating coated veneer ties removes the thermal bridges and breaks the thermal thread. This results in a building envelope having more efficient insulative properties, a thermally-isolated anchoring system, and improved condensate control.
The present invention provides a thermally-isolating coated veneer tie specially-suited for use within a cavity wall. Anchoring systems within cavity walls are subject to outside forces such as earthquakes and wind shear that cause abrupt movement within the cavity wall. Additionally, any materials placed within the cavity wall require the characteristics of low flammability and, upon combustion, the release of combustion products with low toxicity. The present invention provides a coating suited to such requirements, which, besides meeting the flammability/toxicity standards, includes characteristics such as shock resistance, non-frangibility, thermal expansion similar to the underlying metals, low thermal conductivity and transmissivity, and a non-porous resilient finish. This unique combination of characteristics provides a veneer tie well-suited for installation within a cavity wall anchoring system.
In the past, anchoring systems have taken a variety of configurations. Where the applications included masonry backup walls, wall anchors were commonly incorporated into ladder—or truss-type reinforcements and provided wire-to-wire connections with box-ties or pintle-receiving designs on the veneer side.
In the late 1980's, surface-mounted wall anchors were developed by Hohmann & Barnard, Inc., now a MiTEK-Berkshire Hathaway Company, and patented under U.S. Pat. No. 4,598,518. The invention was commercialized under trademarks DW-10®, DW-10-X®, and DW-10-HS®. These widely accepted building specialty products were designed primarily for dry-wall construction, but were also used with masonry backup walls. For seismic applications, it was common practice to use these wall anchors as part of the DW-10® Seismiclip® interlock system which added a Byna-Tie® wire formative, a Seismiclip® snap-in device—described in U.S. Pat. No. 4,875,319 ('319), and a continuous wire reinforcement.
In an insulated dry wall application, the surface-mounted wall anchor of the above-described system has pronged legs that pierce the insulation and the wallboard and rest against the metal stud to provide mechanical stability in a four-point landing arrangement. The vertical slot of the wall anchor enables the mason to have the wire tie adjustably positioned along a pathway of up to 3.625-inch (max.). The interlock system served well and received high scores in testing and engineering evaluations which examined effects of various forces, particularly lateral forces, upon brick veneer masonry construction. However, under certain conditions, the system did not sufficiently maintain the integrity of the insulation. Also, upon the promulgation of more rigorous specifications by which tension and compression characteristics were raised, a different structure—such as one of those described in detail below—became necessary.
The engineering evaluations further described the advantages of having a continuous wire embedded in the mortar joint of anchored veneer wythes. The seismic aspects of these investigations were reported in the inventor's '319 patent. Besides earthquake protection, the failure of several high-rise buildings to withstand wind and other lateral forces resulted in the incorporation of a continuous wire reinforcement requirement in the Uniform Building Code provisions. The use of a continuous wire in masonry veneer walls has also been found to provide protection against problems arising from thermal expansion and contraction and to improve the uniformity of the distribution of lateral forces in the structure.
Shortly after the introduction of the pronged wall anchor, a seismic veneer anchor, which incorporated an L-shaped backplate, was introduced. This was formed from either 12- or 14-gauge sheetmetal and provided horizontally disposed openings in the arms thereof for pintle legs of the veneer anchor. In general, the pintle-receiving sheetmetal version of the Seismiclip interlock system served well, but in addition to the insulation integrity problem, installations were hampered by mortar buildup interfering with pintle leg insertion.
In the 1980's, an anchor for masonry veneer walls was developed and described in U.S. Pat. No. 4,764,069 by Reinwall et al., which patent is an improvement of the masonry veneer anchor of Lopez, U.S. Pat. No. 4,473,984. Here the anchors are keyed to elements that are installed using power-rotated drivers to deposit a mounting stud in a cementitious or masonry backup wall. Fittings are then attached to the stud which include an elongated eye and a wire tie therethrough for disposition in a bed joint of the outer wythe. It is instructive to note that pin-point loading—that is forces concentrated at substantially a single point—developed from this design configuration. This resulted, upon experiencing lateral forces over time, in the loosening of the stud.
There have been significant shifts in public sector building specifications, such as the Energy Code Requirement, Boston, Mass. (see Chapter 13 of 780 CMR, Seventh Edition). This Code sets forth insulation R-values well in excess of prior editions and evokes an engineering response opting for thicker insulation and correspondingly larger cavities. Here, the emphasis is upon creating a building envelope that is designed and constructed with a continuous air barrier to control air leakage into or out of conditioned space adjacent the inner wythe, which have resulted in architects and architectural engineers requiring larger and larger cavities in the exterior cavity walls of public buildings. These requirements are imposed without corresponding decreases in wind shear and seismic resistance levels or increases in mortar bed joint height. Thus, wall anchors are needed to occupy the same ⅜ inch high space in the inner wythe and tie down a veneer facing material of an outer wythe at a span of two or more times that which had previously been experienced.
As insulation became thicker, the tearing of insulation during installation of the pronged DW-10X® wall anchor, see infra, became more prevalent. This occurred as the installer would fully insert one side of the wall anchor before seating the other side. The tearing would occur at two times, namely, during the arcuate path of the insertion of the second leg and separately upon installation of the attaching hardware. The gapping caused in the insulation permitted air and moisture to infiltrate through the insulation along the pathway formed by the tear. While the gapping was largely resolved by placing a self-sealing, dual-barrier polymeric membrane at the site of the legs and the mounting hardware, with increasing thickness in insulation, this patchwork became less desirable. The improvements hereinbelow in surface mounted wall anchors look toward greater insulation integrity and less reliance on a patch.
As concerns for thermal transfer and resulting heat loss/gain and the buildup of condensation within the cavity wall grew, focus turned to thermal isolation and breaks. Another prior art development occurred in an attempt to address thermal transfer shortly after that of Reinwall/Lopez when Hatzinikolas and Pacholok of Fero Holding Ltd. introduced their sheetmetal masonry connector for a cavity wall. This device is described in U.S. Pat. Nos. 5,392,581 and 4,869,043. Here a sheetmetal plate connects to the side of a dry wall column and protrudes through the insulation into the cavity. A wire tie is threaded through a slot in the leading edge of the plate capturing an insulative plate thereunder and extending into a bed joint of the veneer. The underlying sheetmetal plate is highly thermally conductive, and the '581 patent describes lowering the thermal conductivity by foraminously structuring the plate. However, as there is no thermal break, a concomitant loss of the insulative integrity results. Further reductions in thermal transfer were accomplished through the BynaTie® system ('319) which provides a bail handle with pointed legs and a dual sealing arrangement, U.S. Pat. No. 8,037,653. While each prior art invention reduced thermal transfer, neither development provided more complete thermal protection through the use of a specialized thermally-isolating coated veneer tie, which removes thermal bridging and improves thermal insulation through the use of a thermal barrier. The presently presented thermal tie is optionally low profile with a matte-finish coating to provide greater pullout resistance.
Focus on the thermal characteristics of cavity wall construction is important to ensuring minimized heat transfer through the walls, both for comfort and for energy efficiency of heating and air conditioning. When the exterior is cold relative to the interior of a heated structure, heat from the interior should be prevented from passing through the outside. Similarly, when the exterior is hot relative to the interior of an air conditioned structure, heat from the exterior should be prevented from passing through to the interior. The main cause of thermal transfer is the use of anchoring systems made largely of metal, either steel wire formatives, or metal plate components, that are thermally conductive. While providing the required high-strength within the cavity wall system, the use of steel components results in heat transfer.
Another application for anchoring systems is in the evolving technology of self-cooling buildings. Here, the cavity wall serves additionally as a plenum for delivering air from one area to another. The ability to size cavities to match air moving requirements for naturally ventilated buildings enable the architectural engineer to now consider cavity walls when designing structures in this environmentally favorable form.
Building thermal stability within a cavity wall system requires the ability to hold the internal temperature of the cavity wall within a certain interval. This ability helps to prevent the development of cold spots, which act as gathering points for condensation. Through the use of a thermally-isolating coating, the veneer tie obtains a lower transmission (U-value) and thermal conductive value (K-value) and provides non-corrosive benefits. The present invention maintains the strength of the veneer tie and further provides the benefits of a thermal break in the cavity.
In the past, the use of wire formatives have been limited by the mortar layer thicknesses which, in turn are dictated either by the new building specifications or by pre-existing conditions, e.g. matching during renovations or additions the existing mortar layer thickness. While arguments have been made for increasing the number of the fine-wire anchors per unit area of the facing layer, architects and architectural engineers have favored wire formative anchors of sturdier wire. On the other hand, contractors find that heavy wire anchors, with diameters approaching the mortar layer height specification, frequently result in misalignment. This led to the low-profile wall anchors of the inventors hereof as described in U.S. Pat. No. 6,279,283. However, the above-described technology did not address the adaption thereof to surface mounted devices. The combination of each individual tie linked together in a cavity wall setting creates a thermal thread throughout the structure, thereby raising thermal conductivity and reducing the effectiveness of the insulation. The present invention provides a thermal break which interrupts and restricts thermal transfer.
In the course of preparing this Application, several patents, became known to the inventors hereof and are acknowledged hereby:
Pat.InventorIssue Date4,021,990SchwalbergMay, 19774,373,314AllanFebruary, 19834,473,984LopezDecember, 19844,875,319HohmannOctober, 19895,392,581Hatzinikolas et al.February, 19955,456,052Anderson et al.October, 19955,816,008HohmannOctober, 19986,209,281RiceApril, 20016,279,283Hohmann et al.August, 2001
U.S. Pat. No. 4,021,990—B. J. Schwalber—Issued May 10, 1977
Discloses a dry wall construction system for anchoring a facing veneer to wallboard/metal stud construction with a pronged sheetmetal anchor.
U.S. Pat. No. 4,373,314—J. A. Allan—Issued Feb. 15, 1983
Discloses a vertical angle iron with one leg adapted for attachment to a stud; and the other having elongated slots to accommodate wall ties. Insulation is applied between projecting vertical legs of adjacent angle irons with slots being spaced away from the stud to avoid the insulation.
U.S. Pat. No. 4,473,984—Lopez—Issued Oct. 2, 1984
Discloses a curtain-wall masonry anchor system wherein a wall tie is attached to the inner wythe by a self-tapping screw to a metal stud and to the outer wythe by embedment in a corresponding bed joint. The stud is applied through a hole cut into the insulation.
U.S. Pat. No. 4,879,319—R. Hohmann—Issued Oct. 24, 1989
Discloses a seismic construction system for anchoring a facing veneer to wallboard/metal stud construction with a pronged sheetmetal anchor. Wall tie is distinguished over that of Schwalberg '990 and is clipped onto a straight wire run.
U.S. Pat. No. 5,392,581—Hatzinikolas et al.—Issued Feb. 28, 1995
Discloses a cavity-wall anchor having a conventional tie wire for mounting in the brick veneer and an L-shaped sheetmetal bracket for mounting vertically between side-by-side blocks and horizontally on atop a course of blocks. The bracket has a slit which is vertically disposed and protrudes into the cavity. The slit provides for a vertically adjustable anchor.
U.S. Pat. No. 5,456,052—Anderson et al. —Issued Oct. 10, 1995
Discloses a two-part masonry brick tie, the first part being designed to be installed in the inner wythe and then, later when the brick veneer is erected to be interconnected by the second part. Both parts are constructed from sheetmetal and are arranged on substantially the same horizontal plane.
U.S. Pat. No. 5,816,008—Hohmann—Issued Oct. 15, 1998
Discloses a brick veneer anchor primarily for use with a cavity wall with a drywall inner wythe. The device combines an L-shaped plate for mounting on the metal stud of the drywall and extending into the cavity with a T-head bent stay. After interengagement with the L-shaped plate the free end of the bent stay is embedded in the corresponding bed joint of the veneer.
U.S. Pat. No. 6,209,281—Issued Apr. 3, 2001
Discloses a masonry anchor having a conventional tie wire for mounting in the brick veneer and sheetmetal bracket for mounting on the metal-stud-supported drywall. The bracket has a slit which is vertically disposed when the bracket is mounted on the metal stud and, in application, protrudes through the drywall into the cavity. The slit provides for a vertically adjustable anchor.
U.S. Pat. No. 6,279,283—Hohmann et al.—Issued Aug. 28, 2001
Discloses a low-profile wall tie primarily for use in renovation construction where in order to match existing mortar height in the facing wythe a compressed wall tie is embedded in the bed joint of the brick veneer.
None of the above provide a thermally-isolating ceramic or ceramic-based coated anchoring system that maintains the thermal isolation of a building envelope. As will become clear in reviewing the disclosure which follows, the cavity wall structure benefits from the recent developments described herein that lead to solving the problems of thermal insulation and heat transfer within the cavity wall. The veneer tie is modifiable for use with various style wall anchors allowing for interconnection in varied cavity wall structures. The prior art does not provide the present novel cavity wall construction system as described herein below.